UNIVERSITI T E K N O L O G I MARA
ASSESSING IMPACT OF D E M R E S O L U T I O N ON F L O O D
INUNDATION MAPPING
AHMAD IKHWAN BIN ABDUL H A L I M
Thesis submitted in fulfillment of the requirements for the degree of
Bachelor Science of Geomatics
Faculty of Architecture, Planning and Surveying
July 2018
AUTHOR'S D E C L A R A T I O N
I declare that the work in this thesis/dissertation was carried out in accordance with the regulations o f Universiti Teknologi MARA. It is original and is the results o f my own work, unless otherwise indicated or acknowledged as referenced work. This thesis has not been submitted to any other academic institution or non-academic institution for any degree or qualification.
I , hereby, acknowledge that 1 have been supplied with the Academic Rules and Regulations for Post Graduate, Universiti Teknologi MARA, regulating the conduct o f my study and research.
Name o f Student : Ahmad Ikhwan Bin Abdul Halim Student I.D. No. 2015823372
Thesis/Dissertation Title Programme
Faculty
Bachelor o f Surveying Science and Geomatics (Honours) - AP220 Architecture, Planning & Surveying
Assessing Impact of DEM resolution on flood inundation mapping
Signature o f Student
Date July 2018
A B S T R A C T
DEMs can be derived from several sources either through reipote sensing technique (space-home or air-borne survey) or from traditional methods (ground survey). DEMs are characterized by different precision and accuracy based DEM resolution. The use of different resolution o f DEM are obviously effect the result o f flood inundation models. Therefore, the aim o f this paper is to carry out the impact o f flood depth and water extent using original and resample D E M resolution o f low-medium resolution (IFSAR DEM) and low resolution (SRTM DEM). From DEMs, four hydraulic data were extracted cross-section o f a 3.5 km reach o f the Padang Terap River in Kedah, Malaysia. The effect o f different source o f DEMs (and different resolution) and different cross-section interval was investigate by considering the performance o f the hydraulic models in simulation flood water depth as well inundation maps by using one dimensional (1-D) HEC-RAS model. TerraSAR-X image and flood marks had been used to validate the result o f inundated area and flood depths. The outcomes o f this study show that, the use o f different DEMs has serious implications to the result o f hydraulic models. The outcomes also indicated that IFSAR DEM show better prediction in inundated area with value o f F-statistic are increase 1.0 from 70% to 71%
but not in flood depth with the value o f MAE are slightly increase went resampling been made and for SRTM show loss o f model accuracy due to resampling with the F- statistic o f flood extend are decrease drastically with highest value different are 2.0 at cross-section 5 from 26.4 to 24.2 and the highest value different are 0.2 at cross-section 5 from 0.877 to 1.114 o f MAE for flood depth. Moreover, the result for cross-section not give significant impact for flood extent but for flood depth it show that result are quite high different. Cross-section 50 m extract from IFSAR DEM show significantly presented good agreement between measure and predicted of water extend, water depth and water expansion with the value o f F-statistic are 70.56%, value o f MAE for water depth are 0.220 and value o f RMSE for water expansion are 109.046 while the worse are at cross-section 100 with the value o f F-statistic are 68.35%, value o f MAE are for flood depth are 0.240 and value o f RMSE are 158.355. While, for SRTM it show that cross-section are the best cross-section for flood modelling with the value o f F-statistc are 26.40%, value o f MAE for flood depth are 0.878 and value o f RMSE for flood extension are 194.042 while the worse are cross-section 150 with the value of F-statistic are 23.59%, value o f MAE for flood depth are 1.401 and value o f RMSE for flood expansion are 216.049. By proposing the methodology, flood mapping can be provided accurately by considering the error exist in GIS spatial context.
T A B L E O F CONTENT
Page
C O N F I R M A T I O N B Y P A N E L O F E X A M I N E R S i
A U T H O R ' S D E C L A R A T I O N ii S U P E R V I S O R ' S D E C L A R A T I O N iu
A B S T R A C T iv A C K N O W L E D G E M E N T v
T A B L E O F C O N T E N T vi L I S T O F T A B L E S ix L I S T O F F I G U R E S x L I S T O F A B B R E V I A T I O N S / N O M E N C L A T U R E xii
C H A P T E R O N E : I N T R O D U C T I O N
1.1 Research Background 1 1.2 Problem Statement 3 1.3 A i m o f Study 5 1.4 Objective o f Study 5 1.5 Scope o f Study 5 1.8 S ignifieant o f Research 5
1.9 Summary 6
C H A P T E R T W O : L I T E R A T U R E R E V I E W
2.1 Introduction 7
2.2 Definition o f Flood 7
2.2.1 Coastal Flood 7
2.2.2 Urban Flood 8
2.2.3 Flash Flood 8
2.3 Flood Hazard 8
2.4 Flood Inundation 9
2.5 Flood Modelling 10
2.6 HEC-RAS Modelling 11
2.7 Input Data used in Flood Modelling 12 2.7.1 Digital Elevation Model 12
2.7.2 Land-use 15 2.8 Flood Discharge 16
2.8.1 Bjerklie's Equation 17 2.9 Integrated of Hyrdarulic Modelling and GIS in Flood Mapping 17
2.10 Hydraulic Modelling With Different Cross-Section Interval 18 2.11 Hydraulic Modelling with different Digital Elevation Model Resolution 20
2.12 Flood Hazard Map in Malaysia 22
2.13 Summary 22
C H A P T E R T H R E E : M E T H O D O L O G Y
3.1 Introduction 23 3.2 Flow Chart 23 3.3 Preliminary Studies 25
3.3.1 Study Area 25 3.3.2 Software Used 26 3.4 Data Collection 28 3.5 Data Processing 33
3.5.1 Vectorization 33 3.5.2 Resampling 34 3.5.3 Creating Maning' s n Value Table 3 4
3.5.4 RAS Geometry 35 3.6 Data Modelling 37
3.6.1 Hydraulic Modelling 37 3.6.2 Geometric Data 38 3.6.3 Steady Flow Data 39 3.6.4 Steady Flow 40 3.7 Result and Analysis 40
3.8 Summary 41
C H A P T E R F O U R : R E S U L T AND A N A L Y S I S
